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Old March 31st, 2006, 09:10 AM   #1
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Strange FCP Audio Glitches

Hey. I was editing a project yesterday and noticed strange audio glitches - I thought "Oh, probably just some problem with the playback, it'll be fine on the export" - alas, it was not... I was pushing DivX files and the audio glitches were there and in the exact same spots. This lead me to consider that it might have been my capturing method, like maybe the drive I was capturing to was not reading data fast enough and was causing these glitches (though there weren't any in the video, which I think would happen first)... so, I unmounted my project drive, and rebatched my project onto a different drive (7200 rpm firewire)... and the glitches appear still. I checked the tape, they are not on there.

This project was handed to me by someone without any details on how the footage was shot... I don't know what camera, what settings or any of the above so I set the project up as a default easy setup for DV.

If anyone can think of a way to get rid of these glitches or something I'm doing wrong, great... otherwise I'm going to just bump the audio files out and slice them out in protools (something I would rather avoid doing since I'd like to know the root of the problem so I can fix it again should it happen again).

edit: Forgot to mention specs, sorry - capturing using a G4 iBook 1.2GHz /1.25GB RAM through firewire to my maxtor7200RPM drive using my terribly low-tech JVC MiniDV Cam (GR-DVL315U), which, for being a consumer camera, has been a tank for the most part.
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Old March 31st, 2006, 10:53 AM   #2
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what type of audio glitches are they? If the video looks fine, I'd assume it's either something about the actual audio format or it's something that got picked up by the camera.
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Old March 31st, 2006, 01:35 PM   #3
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it sounds like when you pause the video mid playback and it gives you that "repeating" frame glitch... I'll have to export it to give you an idea, probably....

here, i popped a file with an example of what the glitches sound like up to my site -

edit: switched it to an mov for convenience and not wanting to be difficult... heh.

http://jaredsilvia.com/temp/blicious_glitch.mov

regarding audio format, it's just 48/16 standard dv stuff... unless there is something wacky going on with the tape, not sure what else it could be exactly.
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Old March 31st, 2006, 02:54 PM   #4
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If your sure the audio is on the tape, try playback on another camcorder. JVC's can be finicky with tape shot on other units.

To check the JVC, play the tape and check for any blocking( small blocks on right side, most noticable when movement occures), the Jvc may be having a problem.

When the tape is being moved across the heads it is feed around tape guides. If the exit tape guide is out of adjustment, audio can go silent momentarily, this can happen in one particular spot or be intermittent.
Note; you might not see any problems with the video, especially if there isn't any movement on the video( camera panning or people moving).

Jim
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Old March 31st, 2006, 03:10 PM   #5
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James,

I'll try rebatching with a different camera or deck if I can get my hands on one. I haven't had any serious problems with my JVC but it is getting older... so it's not inconceivable that it would be an issue with the unit.

Regarding blocking, I did see some for a moment in a part of one of the clips I pulled in... hmmmmmmm... interesting.

Hehe, another reason why I am going to invest in a DVX100B.... among the millions of others.
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Old May 3rd, 2006, 03:17 PM   #6
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Alas, the glitches continue!! This time with footage shot with a Sony HDR FX1 and captured in using the in-camera HDV to DV downconversion. I captured using the same computer (iBook) with Final Cut 5.0.4 to an external drive directly from the very camera on which the footage was shot, connected via firewire - now, I have a question... is it possible that either:

a.) The Bus speed of my laptop could cause audio glitches where there is no visible video glitch by being not up to par (iBook has a 133 MHz bus)

b.) The low Buffer size of the firewire drive could cause these same audio glitches. The firewire drive is older (over 3 years old) and I can't imagine it has a buffer size anywhere CLOSE to what drives have now.

essentially, if I have to rebatch on a faster system or with a faster drive, that's cool... I just want to eliminate any possible causes.
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Old May 4th, 2006, 01:46 AM   #7
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Quote:
Originally Posted by Jared Silvia
I captured using the same computer (iBook) with Final Cut 5.0.4 to an external drive directly from the very camera on which the footage was shot, connected via firewire -
If you are capturing from a firewire input and writing to a firewire output device on the same firewire bus, you're asking for trouble. Try capturing to the Ibook internal drive. If all is well, you can then move the files over to the external drive. Yes, this method may have worked for you in the past, but there are many variables including remaining space on the drive that could cause trouble.

regards,

-gb-
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Old May 4th, 2006, 08:22 AM   #8
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I guess it looks like that may be my only option from now on, if it is indeed the firewire to comp to firewire problem. Maybe I should consider putting a larger/faster drive in this thing for capturing...
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